Why does exercise sometimes raise your blood sugar?

The short answer is that your body does what it is designed to do. But the mechanics behind it can be difficult to understand.

The first official guidelines for safe training were published in The lancet Journal in 2017. And recently, in 2020, experts published an international position statement on Exercise Glucose Management with Continuous Glucose Monitoring (CGM) in Type 1 Diabetes.

Specifically, these guidelines suggest that “lifting weights, sprints, and vigorous aerobic exercise can promote spikes in BG that can last for hours,” but there is little explanation as to why this happens. And overall, the information can be overwhelming and difficult to follow.

So DiabetesMine reached out to several diabetes and exercise experts to explain what was going on here.

“It is important that your brain and nervous system have access to blood sugar at all times. Because of this, the body has redundant hormones that increase blood sugar, such as glucagon and adrenaline, ”said Sheri R. Colberg, PhD, Professor Emeritus of Exercise Science at Old Dominion University in Norfolk, Virginia, and founder of Diabetesmotion.com. “What happens when you exercise is that glucose-increasing hormones are released to increase the amount of BG released to match what your active muscles are using.”

Colberg admits, “The system is not perfect, however, and intense activity leads to an excessive release of these hormones. When someone does intense but short activities, the BG often increases because too many hormones are released. ”

Ginger Vieira, health trainer, lawyer, and author of several diabetes textbooks, described her experience as a competitive power lifter, personal trainer, and Ashtanga yoga teacher to describe the effects of some of the most common mechanisms for glucose spikes during intense exercise: lactic acid, adrenaline, and fasting.

Lactic acid. The process of gluconeogenesis converts lactic acid into glucose and directs that glucose back to your muscles for energy, ”said Vieira. “This is how the body will fuel your muscles when you work too hard to circulate oxygen and glucose to your cells, as your body would in general aerobics [cardio] A practice.”

Adrenaline. As is common in competitive sports, “your body pours out adrenaline for that ‘fight or flight’ burst of energy,” said Vieira. “Adrenaline tells your liver to release stored glucose in the form of glycogen to provide the extra fuel it needs for a ‘fight’ or football game. This can easily raise your blood sugar to over 100 points. ”

Fasting exercise. Exercising on an empty stomach can cause glucose spikes, especially right after you wake up. Exercise can exacerbate the so-called dawn phenomenon when, in the early hours of the morning, “your liver releases stored glucose along with morning hormones to give your brain the fuel it needs to function,” explains Vieira.

It is clear that many mechanisms can cause glucose levels to rise during exercise. No wonder it can be so difficult to know what to do to get your glucose levels back down.

One of the first things you may ask yourself is whether there are “good” and “bad” exercises for people with diabetes … like in “Maybe I Should Just Avoid the” Bad “”.

Christel Oerum, certified personal trainer and founder of Diabetes Strong and Diabetic Foodie, offered an alternative way of looking at this question. “Think of it this way: your body just wants to help you, it wants you to be successful. So when you do certain types of workouts, mostly anaerobic exercises, your body is trying to make sure you have the energy to be successful. It does this by releasing hormones that allow energy in the form of glucose to be released into your bloodstream. And that can increase blood sugar. ”

This response isn’t limited to people with diabetes. Vieira confirmed that “exactly the same process goes on in a non-diabetic body, but your body makes extra insulin to deal with the extra glucose.”

“Just because blood sugar levels go up in certain sports doesn’t mean they are bad exercise or that the increase is for a bad reason,” added Vieira. “This is the body’s normal response to various factors that can primarily occur during anaerobic exercise – such as weight lifting, sprinting, spinning classes, competitive moments, etc.

Since this is anaerobic training that causes BG spikes during activity, you might think that the answer might be to avoid sprinting, resistance training, or other anaerobic activity.

“But that would be a shame because strength training is fantastic for diabetes management,” Oerum noted. “Most people will find that their insulin sensitivity increases afterwards, and most of the time the blood sugar drops on its own.”

Oerum suggests combining anaerobic with aerobic exercise. This approach offsets the effects and usually results in blood glucose levels dropping shortly after completing the training session.

Obviously, if your training goal is to lower your blood sugar levels right away, then aerobic exercise such as walking, swimming, or skipping rope are effective choices.

Ultimately, it is the presence of insulin that determines when and how quickly blood glucose levels drop.

So try to assess the situation in terms of your insulin intake or insulin on board (IOB). Maybe you didn’t get enough insulin to cover a meal before your workout, or maybe you are exercising shortly after you wake up when the IOB is at its natural low.

Blood sugar spikes caused by adrenaline rushes can be difficult to predict because they mostly occur in the middle of an exercise session. This means that instead of treating the spike right away, you will most likely have to wait and take extra insulin afterwards.

More insulin is also needed if the spike is caused by fasting exercise. Some extra insulin is needed, but not enough to result in a hypoglycemic episode during or after exercise.

Unfortunately, there are no hard and fast rules for making these insulin dosage adjustments. Every situation for every person requires an individual response. It is best to work with your medical team to determine the best response for you.

That being said, both Vieira and Oerum recommend taking notes and tracking your experiences so that you can learn from your experiences. You may find that certain activities have a predictable BG spike effect for you personally. Over time, you can develop a routine that will enable you to both get the exercise you want and anticipate those frustrating peaks.

Many people who wear an insulin pump learn to use custom “temporary basal” settings to increase (or decrease) background insulin during certain exercise routines. This can help compensate for the increase so that you do not have to take a large bolus dose of insulin afterwards.

You can also experiment with your own ideal “starting glucose level” before starting your workout. The 2017 guidelines provide general recommendations for “target levels” of 126 to 180 mg / dL and taking 10 to 20 grams of fast-acting glucose before starting. You need to keep track of your own experiences in order to know what is the ideal of you.

Hopefully, once you understand why BG levels rise during exercise and accept that it isn’t necessarily a bad thing, you will hopefully notice a mental shift away from frustration and disappointment, towards appreciating what you are doing in response can.

While there is no one-size-fits-all guide, you know that over time, you can build an exercise routine that includes small amounts of glucose and insulin dosing that will keep your BG levels under control.